Search

Background and Aims Trees interconnected through functional root grafts can exchange resources, but the effect of exchange on trees remains under debate. A mechanistic understanding of resource exchange via functional root grafts will help understand their ecological implications for tree water exchange for individual trees, groups of trees and forest stands. Methods To identify the main patterns qualitatively describing the movement of sap between grafted trees, we reviewed the available literature on root grafting in woody plants that focus on tree allometry and resource translocation via root grafts. We then extended the BETTINA model, which simulates mangrove (Avicennia germinans) tree growth on the individual tree scale, to synthesize the available empirical information. Using allometric data from a field study in mangrove stands, we simulated potential water exchange and analysed movement patterns between grafted trees. Key Results In the simulations, relative water exchange ranged between −9.17 and 20.3 %, and was driven by gradients of water potential, i.e. differences in tree size and water availability. Moreover, the exchange of water through root grafts alters the water balance of trees and their feedback with the soil: grafted trees that receive water from their neighbours reduce their water uptake. Conclusions Our individual-tree modelling study is a first theoretical attempt to quantify root graft-mediated water exchange between trees. Our findings indicate that functional root grafts represent a vector of hydraulic redistribution, helping to maintain the water balance of grafted trees. This non-invasive approach can serve as a basis for designing empirical studies to better understand the role of grafted root interaction networks on a broader scale.

Conservation biology emerged as a crisis discipline in the twentieth century amongst an increasing awareness of pollution and habitat loss. Since the early 2000s, societal and monetary benefits of nature were added to the narrative for biodiversity conservation. Using text mining, we show that authors now favour ecosystem-services over a crisis framing in scientific publications on coastal habitats. This may signal a shift in conservation science from a crisis to a services discipline despite continuing habitat loss. We discuss whether authors should more critically assess what conservation narrative they deploy and what consequences this may have for conservation action.

Funder: Agua Salud Project, Funder: U.S. Department of Energy; Id: http://dx.doi.org/10.13039/100000015, Funder: CAPES; Id: http://dx.doi.org/10.13039/501100002322, Data capturing multiple axes of tree size and shape, such as a tree's stem diameter, height and crown size, underpin a wide range of ecological research-from developing and testing theory on forest structure and dynamics, to estimating forest carbon stocks and their uncertainties, and integrating remote sensing imagery into forest monitoring programmes. However, these data can be surprisingly hard to come by, particularly for certain regions of the world and for specific taxonomic groups, posing a real barrier to progress in these fields. To overcome this challenge, we developed the Tallo database, a collection of 498,838 georeferenced and taxonomically standardized records of individual trees for which stem diameter, height and/or crown radius have been measured. These data were collected at 61,856 globally distributed sites, spanning all major forested and non-forested biomes. The majority of trees in the database are identified to species (88%), and collectively Tallo includes data for 5163 species distributed across 1453 genera and 187 plant families. The database is publicly archived under a CC-BY 4.0 licence and can be access from: https://doi.org/10.5281/zenodo.6637599. To demonstrate its value, here we present three case studies that highlight how the Tallo database can be used to address a range of theoretical and applied questions in ecology-from testing the predictions of metabolic scaling theory, to exploring the limits of tree allometric plasticity along environmental gradients and modelling global variation in maximum attainable tree height. In doing so, we provide a key resource for field ecologists, remote sensing researchers and the modelling community working together to better understand the role that trees play in regulating the terrestrial carbon cycle.

Mangrove forests are highly productive ecosystems that sustain marine life, including fish communities. This study aimed to analyse mangrove characteristics, physicochemical parameters, nutrient and primary production derived from mangrove litter and estimate the fish production. The study was conducted at five mangrove sites in North Sumatra and the Aceh Provinces, Indonesia. Two sites represented natural forest at North Sumatra and Aceh (Jaring Halus and Langsa). In comparison, two sites were mangroves converted into oil palm plantations (Pulau Sembilan and Pulau Kampai, North Sumatra). The fifth site was a mangrove forest converted into aquacultural ponds (Percut Sei Tuan, North Sumatra). The study displays the dissemination of mangrove species in five different mangrove sites showing diversity. Avicennia spp found in estuarine near a coastal area, Rhizophora spp spread across the sites, and Sonneratia spp were more likely to occur in the mouth of the upstream river. Litter production at the present study site was dominated by Rhizophora spp., followed by Avicennia spp. This finding was very closely related to the nutrients resulting from litter decomposition in the mangrove ecosystem. The primary production value of 870-1,747 g C m-2 year had a significant role as the beginning of the estuary food chain. Our results show a close association between fish productivity and mangrove management, and conservation status. The highest fish production was found in the well-preserved forests (Jaring Halus and Langsa), followed by the sites converted to palm oil plantations (Pulau Sembilan and Pulau Kampai). At the same time, the least fishing productivity was identified at the fishing ponds (Percut Sei Tuan). The present study provides further evidence of the significant role of mangrove ecosystems for fisheries and calls for effective restoration programs to support local food security along the coast of Indonesia.

Hydrological monitoring is crucial for management and research in coastal wetlands. However, long-term monitoring is scarce due to the high cost of conventional hydrological equipment. The development of open-source and low-power sensors over the past decade presents an opportunity for enabling long-term, high spatial resolution monitoring of hydrodynamics in the intertidal zone. Here, we present the design, calibration, and application of one such sensor: the Mini Buoy. The Mini Buoy is a battery-powered accelerometer and data logger, contained in a standard centrifuge tube. The Mini Buoy floats upright when inundated, and moves freely about a tether anchored to the substrate. Acceleration is measured along a single axis of the buoy, and motion along the axis is used to measure inundation, currents, and waves. Deployments of up to 6 months are possible, and the buoy can measure current and wave orbital velocities as low as 0.05 m/s. Mini Buoys cost less than €350 to assemble, and the materials are globally available. We present the successful application of Mini Buoys in four contrasting scenarios: (1) characterising waves under calm and stormy conditions; (2) linking saltmarsh erosion-expansion patterns with hydrological exposure; (3) identifying high-resolution spatial variability of waves and currents along a saltmarsh edge; and (4) assessing the suitability of former aquaculture ponds for mangrove restoration. Mini Buoys are also being deployed along mangrove fringes across Vietnam, India, and Bangladesh, in order to detect thresholds in hydrodynamic forcing responsible for triggering erosion or progradation events. Mini Buoys offer an exciting and novel tool for coastal management worldwide.

Ecosystem functioning of habitats at land-water interfaces, such as riparian forests and intertidal salt marshes or mangroves is predominantly driven by inundation. Whereas seasonality of ecological processes (i.e. phenology) and of hydrological extremes/events have been relatively well studied independently from each other their interdependence remains largely unknown. Filling this knowledge gap may become especially important in a changing climate as the timing of ecological and abiotic processes is already changing, often independently from each other. As these ecosystems are increasingly praised as Nature-based Solutions, predicting the ecosystem functioning of riparian forests and coastal wetlands under future climate change is crucial.Here, we will highlight the importance of match and mismatch of ecological and hydrological processes through a range of experiments and field observations in coastal wetlands from the single seedling to the ecosystem level. For riparian floodplains of Europe, we will show how the temporal relationships between flooding and thermal growing season have already changed in past decades, with currently unknown consequences. Finally, we will showcase methodological advances in field monitoring to better study these timing effects and offer conceptual insights to identify tipping points of ecosystem change along land-water interfaces.This presentation will focus on UPH ‘interfaces’ and ‘variability’.

Rampant global urbanization has led to a drastic reduction in the global extent of many coastal landform habitats as a result of land reclamation, overexploitation of habitats, hard engineering, and/or extension of built infrastructure into the sea. Saltmarshes are dynamic landforms where ecological, geomorphological, and hydrodynamic systems interact to create highly productive and societally valuable intertidal landforms in sediment rich estuaries and open coasts. The diversity of coastal habitat types from rocky shores, beaches, dunes, muddy shores, and wetlands means that these habitats provide a wide spectrum of ecosystem services. Coasts are dynamic transitional zones that are under increasing pressure both from rapid urbanization and from climate related impact, including sea-level rise and more intense storms. On undeveloped or lightly developed coasts allowing coastal landforms to move inland may prove to be the most sustainable and least-cost option in the medium to long term.

Aim:\ud \ud Tree crowns determine light interception, carbon and water exchange. Thus, understanding the factors causing tree crown allometry to vary at the tree and stand level matters greatly for the development of future vegetation modelling and for the calibration of remote sensing products. Nevertheless, we know little about large‐scale variation and determinants in tropical tree crown allometry. In this study, we explored the continental variation in scaling exponents of site‐specific crown allometry and assessed their relationships with environmental and stand‐level variables in the tropics.\ud \ud Location:\ud \ud Global tropics.\ud \ud Time period:\ud \ud Early 21st century.\ud \ud Major taxa :\ud \ud Woody plants.\ud \ud Methods:\ud \ud Using a dataset of 87,737 trees distributed among 245 forest and savanna sites across the tropics, we fitted site‐specific allometric relationships between crown dimensions (crown depth, diameter and volume) and stem diameter using power‐law models. Stand‐level and environmental drivers of crown allometric relationships were assessed at pantropical and continental scales.\ud \ud Results:\ud \ud The scaling exponents of allometric relationships between stem diameter and crown dimensions were higher in savannas than in forests. We identified that continental crown models were better than pantropical crown models and that continental differences in crown allometric relationships were driven by both stand‐level (wood density) and environmental (precipitation, cation exchange capacity and soil texture) variables for both tropical biomes. For a given diameter, forest trees from Asia and savanna trees from Australia had smaller crown dimensions than trees in Africa and America, with crown volumes for some Asian forest trees being smaller than those of trees in African forests.\ud \ud Main conclusions:\ud \ud Our results provide new insight into geographical variability, with large continental differences in tropical tree crown allometry that were driven by stand‐level and environmental variables. They have implications for the assessment of ecosystem function and for the monitoring of woody biomass by remote sensing techniques in the global tropics.

Acquiring in-situ data of tidal flooding is key for the successful restoration planning of intertidal wetlands such as salt marshes and mangroves. However, monitoring spatially explicit inundation time series and tidal currents can be costly and technically challenging. With the increasing availability of low-cost sensors and data loggers, customized solutions can now be designed to monitor intertidal hydrodynamics with direct applications for restoration and management. In this study, we present the design, calibration, and application of the Mini Buoy, a low-cost bottom-mounted float containing an acceleration data logger for monitoring tidal inundation characteristics and current velocities derived from single-axis equilibrium acceleration (i.e. logger tilt). The acceleration output of the Mini Buoys was calibrated against water-level and current velocity data in the hypertidal Bay of Fundy, Canada, and in a tidally reconnected former aquaculture pond complex in North Sumatra, Indonesia. Key parameters, such as submersion time and current velocities during submergence can be determined over several months using the Mini Buoy. An open-source application was developed to generate ecologically meaningful hydrological information from the Mini Buoy data for mangrove restoration planning. We present this specific SE Asian mangrove restoration application alongside a flexible concept design for the Mini Buoy to be customized for research and management of intertidal wetlands worldwide.

(1,2) In this theoretical study, we apply MesoFON, a field-calibrated individual-based model of mangrove forest dynamics, and its Lotka–Volterra interpretations to address two questions: (a) Do the dynamics of two identical red mangrove species that compete for light resources and avoid inter-specific competition by lateral crown displacement follow the predictions of classical competition theory or resource competition theory? (b) Which mechanisms drive the dynamics in the presence of inter-specific crown plasticity when local competition is combined with global or with localized seed dispersal? (3) In qualitative support of classical competition theory, the two species can stably coexist within MesoFON. However, the total standing stock at equilibrium matched the carrying capacity of the single species. Therefore, a “non-overyielding” Lotka–Volterra model rather than the classic one approximated best the observed behavior. Mechanistically, inter-specific crown plasticity moved heterospecific trees apart and pushed conspecifics together. Despite local competition, the community exhibited mean-field dynamics with global dispersal. In comparison, localized dispersal slowed down the dynamics by diminishing the strength of intra-/inter-specific competition and their difference due to a restriction in the competitive race to the mean-field that prevails between conspecific clusters. (4) As the outcome in field-calibrated IBMs is mediated by the competition for resources, we conclude that classical competition mechanisms can override those of resource competition, and more species are likely to successfully coexist within communities., SCOPUS: ar.j, info:eu-repo/semantics/published

Los manglares de Laguna de Términos, Campeche han sido afectados por la pérdida de la conexión hidrológica durante el paso de tormentas y huracanes. El objetivo de este trabajo fue evaluar la regeneración natural del manglar en un área degradada, después de haber implementado acciones de restauración hidrológica. Se establecieron tres sitios de muestreo con diferentes tiempos de restauración (1 año - 3 años) y un sitio de manglar natural conservado como referencia. El muestreo se realizó en los años 2014 a 2015. Se evaluó densidad, altura, sobrevivencia y tasa de crecimiento de las plántulas, así como las características ambientales. La relación entre la vegetación y las características ambientales se realizaron mediante regresiones lineales simples y un análisis de escalamiento multidimensional. Para determinar la dispersión de propágulos respecto a los manglares naturales, se generó un modelo lineal mixto de la densidad de propágulos vs. la distancia y el tiempo de restauración. Los resultados demostraron que la distancia respecto a los manglares naturales afectó la densidad de los propágulos. La concentración de fosfato se relacionó con la sobrevivencia de las plántulas; mientras que la concentración de amonioy la concentración de sulfuro se relacionaron negativamente con la densidad de las plántulas. Las acciones de restauración hidrológica influyeron en el establecimiento y desarrollo de la vegetación de manglar; por lo tanto, las zonas de manglar natural y la restauración hidrológica facilitaron la dispersión de los propágulos hacia las zonas degradadas, resaltando la importancia de contemplar estas áreas naturales dentro de los proyectos de restauración.

1. Crown displacement in trees is an adaptive response driven by neighbours that optimizes space use and reduces competition. But it can also be the result of wind force. Although morphological responses to neighbours have been well studied, the interplay between neighbours and wind in driving crown shape, and the implications for plant interactions remain poorly understood. However, it is crucial to predict such changes in vegetation structure and function under the scope of global change. We test the hypothesis that aboveground interactions are reduced with increasing soil stress and that wind becomes the main driver of crown shape in mangrove forests.\ud 2. We investigated the effect of neighbours and wind intensity and direction on crown displacement of mangrove canopy and below canopy trees along a salinity gradient, and assessed crown asymmetry for three mangrove tree species, as well as the contribution of crown displacement on reducing crown‐projected area overlap and thus neighbourhood competition.\ud 3. Results show that crown displacement of canopy trees is strongly influenced by winds at all salinities. At low salinities, competition for space accounted for 48% of crown displacement away from neighbours, compared to 49% found for the synthetized effects of wind and neighbours. While trees below the canopy displace their crowns away from their neighbours, no response to wind could be detected. This can be due to the wind protection conferred by a dense canopy stand related to bigger crowns that effectively reduce wind drag. At higher salinities, there was a reduction in canopy overlap due to crown displacement, which suggests reduced aboveground plant interactions with increasing soil stress.\ud 4. While neighbourhood avoidance is a fundamental strategy for optimal light foraging, this study shows that wind strength and directionality are main drivers of crown shape with increasing stress and highlights their potential influence in plant interactions and forest structure, pointing to an increased susceptibility of trees to disturbances that should be further studied.

This study presents mesoFON, an individual-based mangrove forest dynamics model that advances beyond current models by describing crown plasticity of mangrove trees. The crown plasticity routines take advantage of the fields-of-neighborhood (FON) approach and account for the trunk bending and the differential side branch growth mechanism. Competition for above-/below-ground resources is dealt with separately in this model. Offspring production depends on tree growth and rises with tree ontogeny. An extensive sensitivity analysis revealed that mesoFON resembles the behavior of known mangrove forest dynamics and is ready for application. In this study we exposed two plant functional types (PFTs) of the red mangrove (Rhizophora mangle L.) either in monoculture or as a community to two disturbance regimes, namely (1) without disturbances and (2) with hurricane impacts returning every 5 years. While one functional type possesses plastic crowns, the other PFT has rigid crowns. For the first time, long-term interaction of lateral crown displacement and disturbance was examined using a comprehensive comparative analysis including point patterns and canopy coverage. In the monoculture experiments disturbance strongly promoted the beneficial effects of crown plasticity. Without disturbance crown movements merely increased stand-based stem volume by 6.7% despite considerable displacement distances. We attribute this to the overall high competitive strength that constrained the effects of plasticity in the dense stands. Yet, in disturbed stands the plastic behavior raised stem volume and tree density by 12.5% and 7.5%, respectively, as a result of substantially reduced local competition (by 20.1%). In this treatment crown shifts are particularly advantageous because of their contribution to gap closure. Generally, the Clark Evans aggregation index of crown centers tended to be higher than that of stem bases indicating a more regular distribution of crown centers. The same was true for the canopy coverage of crowns located at their centers implying better space usage by shifted crowns. Pair-correlation functions revealed a plasticity-induced trend toward more regular distribution at low tree-to-tree distances and less aggregation at intermediate distances. The trend was stronger in disturbed communities. The plastic PFT was finally able to out-compete the rigid PFT in all community experiments. Hurricane impacts, however, accelerated the time to the extinction of the rigid PFT by a factor of 2.4.

Morphological plasticity helps plants to cope to environmental conditions. Allometric responses of the mangrove Avicennia germinans to increasing salinity are easily detectable when focusing on the top height trees. Several studies show that mangrove trees possess high species- and site-related trait allometry, suggesting large morphological plasticity that might be related to environmental conditions, but the causes of such variation are not clearly understood and systematic quantification is still missing. Both aspects are essential for a mechanistic understanding of the development and functioning of forests. We analyzed the role of salinity in the allometric relations of the mangrove Avicennia germinans, using: (1) the top height trees (trees with the largest diameters at breast height, which reflect forest properties at the maximum use of resources); (2) the slenderness coefficient (which indicates competition and environmental conditions); and (3) the crown to DBH ratio. These standard tools for forest scientists dealing with terrestrial forests are suitable to analyze the plastic responses of mangroves to salinity. First, the top height trees help to recognize structural forest properties that are not detectable when studying the whole stand. Second, we found that at salinities above 55 ‰, trees are less slender and develop wider crowns in relation to DBH than when growing at lower salinities. Our results suggest a significant change in allometric traits in relation to salinity, and reflect the plastic responses of tree traits in response to environmental variation. Understanding the plastic responses of plants to their environment can help to better model, predict, and manage forests in changing environments.

Models based on allometric responses to competing neighbours and environmental conditions in mangrove forests are increasingly available. However, the improvement of these models requires a mechanistic understanding of how individual trees allocate biomass. This study introduces a new tree model (BETTINA) focusing on this issue. It is designed to investigate the response of trees in terms of biomass allocation patterns to environmental conditions. Additionally, it is suitable as a component of an individual-based mangrove stand model. BETTINA describes the plasticity of trees in growth patterns depending on their below-ground resource uptake. In contrast to the existing mangrove stand models, BETTINA focusses explicitly on the processes leading to variation in resource availability. Based on the physical principle of osmotic potential of solutions, the direct influence of salinity on plant water availability is considered. Allometric model parameters are not restricted to only the above-ground measures of trees’ traits (such as stem diameter and height), but also characterize below-ground biomass. Within BETTINA these measures are not limited to predefined empirical maximum values, but are the result of and depend on environmental conditions. The model is suitable to explain allometric measures and relations in dependence on total plant size and environmental conditions (for now salinity and light), and has a great potential for a physiologically and physically based improvement of plant component related biomass estimations.

This work presents the development of a low-cost method to measure the length cable roots of black mangrove (Avicennia germinans) trees to define the boundaries of central part of the anchoring root system (CPRS) without the need to fully expose root systems. The method was tested to locate and measure the length shallow woody root systems. An ultrasonic Doppler fetal monitor (UD) and a stock of steel rods (SR) were used to probe root locations without removing sediments from the surface, measure their length and estimate root-soil plate dimensions. The method was validated by comparing measurements with root lengths taken through direct measurement of excavated cable roots and from root-soil plate radii (exposed root-soil material when a tree tips over) of five up-rooted trees with stem diameters (D130) ranging between 10 and 50 cm. The mean CPRS radius estimated with the use of the Doppler was directly correlated with tree stem diameter and was not significantly different from the root-soil plate mean radius measured from up-rooted trees or from CPRS approximated by digging trenches. Our method proved to be effective and reliable in following cable roots for large amounts of trees of both black and white mangrove trees. In a period of 40 days of work, three people were capable of measuring 648 roots belonging to 81 trees, out of which 37% were found grafted to other tree roots. This simple method can be helpful in following shallow root systems with minimal impact and help map root connection networks of grafted trees.

Microbial processes are key elements in determining the productivity of mangroves, and reductions in these processes reflect the loss of microbial biodiversity and function due to fabricated disturbances. Because nitrogen is a major limiting nutrient for the productivity of these ecosystems, the goal of this study was to determine profiles of inorganic nitrogen combined with several environmental parameters, all in relation to the degree of long-term hydraulic impairment of a tropical, monospecific black mangrove (Avicennia germinans) forest that showed degradation ranging from total loss of mangrove cover to no disturbance. N2-fixation, oxygen levels, and nitrite contents decreased significantly with the severity of the disturbance, and almost null levels were reached in the completely degraded zone, whereas salinity achieved very high values. Concomitantly, total N, ammonium, and P contents and ammonia volatilization increased significantly. Pore-water temperature and pH increased moderately. Other soil physical properties (sand, silt, clay, organic matter, and total C), which varied among the sampling sites, were not correlated with the level of disturbance. Principal component analyses, including environmental and biological parameters, suggested that the most significant finding was the considerable loss of N2-fixation with increasing impairment, which was concomitant with significant increases in volatilization of ammonia and salinity. The results show that microbial N-cycling processes are highly sensitive to salinity and to man-made disturbances that modify the water level and flow.

Although several damaged mangrove ecosystems have been restored worldwide, so far, it has not been established whether a restored mangrove system regains all the functional properties of preserved mangroves. This study measured nitrogen fixation as an indicator of whether disturbed mangroves that were reforested or naturally regenerated fully recovered from this disturbance at a functional level. Rates of nitrogen fixation were measured for one year in impaired, preserved, reforested, and naturally regenerated mangroves dominated by the black mangrove (Avicennia germinans). There was no significant difference in rates of nitrogen fixation among preserved and adjacent reforested and naturally regenerated mangroves, but a significant reduction occurred in an impaired mangrove. Nitrogen fixation was mainly controlled by pH, salinity, and temperature. The highest rates of nitrogen fixation occurred in summer at pH values less than 6.4, whereas the impaired mangrove had higher pH and salinity and had very low nitrogen fixation activity. These results suggest that nitrogen fixation can be used as an ecological indicator of the success of reforestation and as a sensitive measure of perturbations in mangroves.